Description

1) Take a clean new Tor Browser 7
2) Start it and configure an obfs4 proxy (choosing the built-in default option)
3) Shut it down
4) Restart it and choose "Open Setting"
5) Click "Connect"
6) You are greeted with

You have configured Tor bridges or you have entered local proxy settings. To
make a direct connection to the Tor network, these settings must be removed.

7) Click on the "Remove Settings and Connect"-button
8) After start-up look at the Tor network settings (green onion -> Tor Network Settings...) and you'll see that bridges are still configured.